| A serious disease called "feline hyperthyroidism" has | | | | Perhaps the most interesting wrinkle in this recent |
| risen to epidemic proportions since the first cases | | | | study is that PBDEs were also found in cat food. For |
| were diagnosed in 1979. It is a worldwide | | | | two major types of PBDEs, high levels were found in |
| phenomenon, though worse in the U.S. than other | | | | canned food, especially fish- or seafood-based cat |
| countries. Hyperthyroidism (hyper = too much, | | | | foods. However, high levels of other PBDEs were |
| thyroid = a hormone-making gland), is seen mostly in | | | | found in dry cat food. |
| older cats age 10 or more. Thyroid hormone | | | | The combination of PBDEs, can liner chemicals, and |
| regulates the body's basic metabolic rate. Too much | | | | excess iodine may be too much for many cats to |
| of it is like drinking too much coffee-it speeds up | | | | handle. However, plenty of outdoor cats who never |
| every reaction in the body. | | | | eat canned food can also develop the disease-so |
| The problem is typically a benign thyroid tumor. | | | | other factors that haven't been discovered yet are |
| Because the tumor cells are relatively normal, they | | | | likely to be involved. For instance, many holistic |
| continue to produce thyroid hormones, resulting in a | | | | veterinarians also believe that, because this disease is |
| high level in the blood. The thyroid regulates the | | | | fairly new but rapidly reaching epidemic proportions, |
| body's metabolic rate, so this increase is sort of like | | | | that vaccines may also be a factor. |
| drinking espresso around the clock. Symptoms include | | | | What can you do to minimize the risk for your cat? |
| increased appetite, weight loss despite eating more, | | | | Well, it wouldn't be smart to push your cat |
| increased heart rate, anxiety or "hyper" behavior, | | | | outdoors-the dangers outside are far worse, and |
| howling at night, increased thirst and urination, | | | | most of them will kill your cat long before the age |
| vomiting, and diarrhea. Not all cats will have all | | | | where she's at risk for thyroid disease. Ripping out all |
| symptoms, and about 20% of hyperthyroid cats will | | | | your carpets and throwing away your furniture |
| be sluggish and depressed instead of hyperactive. | | | | probably isn't all that practical, either! |
| Untreated, hyperthyroidism can cause a serious heart | | | | Feeding canned food is very important to an older |
| problem called hypertrophic cardiomyopathy that will | | | | cat's overall health, but it may be wise to stick to |
| ultimately be fatal. | | | | poultry, beef and lamb flavors that don't contain liver, |
| Causes. Many theories have been proposed to | | | | giblets, or by-products. If possible, get the larger cans |
| explain the dramatic rise in feline thyroid disease. | | | | that don't have a pop-top. |
| Because it affects so many cats, the focus has been | | | | Treatments. There are three primary treatment |
| on widespread, environmental causes. Studies have | | | | options for hyperthyroidism: |
| found several suspects in cat food: | | | | - Methimazole (Tapazole) is a medication that can be |
| - One theory implicates the large excess of iodine | | | | given in tablet form (the tiny tablet can be crushed |
| found in many cat foods. Humans can develop | | | | and mixed into wet food) or as a topical gel that you |
| hyperthyroid disease from too ingesting much iodine; | | | | rub on the inside of the cat's ears (ideal for |
| might cats do the same? Iodine is difficult and | | | | non-pillable cats). It requires frequent blood tests for |
| expensive to test for; instead, pet food makers | | | | the first few weeks as the dosage is adjusted to fit |
| routinely add extra, just to make sure that minimums | | | | the cat, and then every six months to make sure |
| are met. But how much is too much? So far, nobody | | | | the dose remains appropriate. Occasionally, cats |
| knows; and nobody is really looking. | | | | become allergic to the medication. While this is initially |
| - Several studies found an increased likelihood of | | | | the least expensive option, maintenance can become |
| developing thyroid disease in cats who eat a lot of | | | | costly over time. |
| canned food. Specifically, they found a higher | | | | - Thyroidectomy is the surgical removal of the |
| incidence of hyperthyroidism in cats that ate fish or | | | | thyroid glands. Cats actually have two thyroids, one |
| "giblet" canned foods. "Giblet" is another name for | | | | on either side of the throat. Often only one is |
| organ meats commonly listed on pet food labels as | | | | involved and can be safely removed. However, there |
| "by-products." Better-quality, natural cat foods do not | | | | is a significant risk that the second gland will ultimately |
| contain by-products, although some include specific | | | | develop disease and need to be removed later. |
| organ meats like liver. Just what it is in these foods | | | | Removing the thyroids is no big deal to an |
| that is problematic is unknown. | | | | experienced surgeon, but there is one major problem: |
| - Recent research suggests that the culprit may be a | | | | four tiny parathyroid glands that are closely attached |
| chemical (bisphenol A and similar compounds) found in | | | | to the thyroids. Removing or damaging the |
| can linings of easy-open "pop-top" cans that can | | | | parathyroids can result in severe, even |
| leach out into the food and cause toxicity (the | | | | life-threatening problems with calcium balance. |
| smaller the can, the more chemical exposure the | | | | Because of the way the thyroid glands develop in |
| food has). However, there are at least 25 different | | | | the fetus, there can be thyroid cells scattered here |
| types of can linings, and the particular type used by a | | | | and there that can also become cancerous. A cat |
| manufacture may change over time. It is difficult to | | | | who has had both thyroids removed can therefore |
| know which foods may be affected, and to what | | | | still become hyperthyroid again. These secondary |
| degree. The FDA, however, has stated that the | | | | tumors can form inside the chest where they cannot |
| amount of chemicals that may leach into the food is | | | | be surgically removed. |
| unlikely to cause disease. | | | | - Radioactive Iodine is the most definitive treatment. |
| - A new study that recently captured media | | | | The thyroid uses iodine to make its hormones, and |
| attention suggests that fire-retardant chemicals | | | | accumulates large amounts of iodine. A single injection |
| known as PBDEs may be a factor in feline | | | | of radioactive iodine will be hoarded by thyroid cells |
| hyperthyroidism-even though the study itself clearly | | | | and kill them, theoretically curing the disease |
| states "no association was detected between | | | | permanently. Most cats tolerate this procedure well, |
| hyperthyroid cats and PBDE levels." The authors note | | | | and most do not need thyroid supplementation. The |
| that PBDEs were introduced at about the same time | | | | downside? The up-front cost is very expensive, and |
| hyperthyroidism was first described in cats. California | | | | regulations require that the cat be kept in the hospital |
| was particularly aggressive in promoting these | | | | for 7-10 days. However, dealing decisively with the |
| life-saving fabrics, which could explain why the | | | | problem may save money in the long run because no |
| veterinary school at U.C. Davis saw so many early | | | | further treatment is needed in most cats. |
| cases of hyperthyroid disease in cats. Additionally, the | | | | Complications |
| rate of feline hyperthyroidism has roughly paralleled | | | | Since hyperthyroid cats are typically older, many also |
| the use of PBDEs in other countries. This particular | | | | have underlying kidney disease that may or not be |
| study looked at only 23 cats (less than half with | | | | obvious. The increased blood flow caused by |
| hyperthyroid disease; and the case controls were not | | | | hyperthyroidism can actually help the kidneys and |
| well-matched in age or gender. | | | | keep them functioning at a fairly normal rate. |
| The main route of exposure in cats was | | | | Lowering the thyroid levels (by any treatment) |
| hypothesized to be the PBDEs contained in carpets, | | | | lowers blood pressure and blood flow. This can |
| upholstery, and mattresses-and the dust mites that | | | | "unmask" kidney disease that was always there but |
| live in these fabrics. Electronic equipment, which | | | | not detectable. |
| attracts dust, is also a suspect. Since cats often | | | | Because surgery and iodine treatments are |
| sleep on carpets, sofas, chairs, mattresses, and nice | | | | irreversible, a few weeks of treatment with |
| warm TVs and stereos, their exposure could be high | | | | methimazole is usually a prerequisite. A cat with both |
| and prolonged. Subsequent grooming would then | | | | kidney disease and hyperthyroidism is a challenge to |
| cause the cat to ingest a fairly large amount of dust. | | | | manage; you'll need to work closely with your |
| This may explain why hyperthyroidism is also more | | | | veterinarian if this is the case. |
| common in indoor cats. | | | | |